Field of the Invention
The present invention relates to methods for identifying edges on a camshaft target for an internal combustion engine.
More particularly, the invention relates to a process for identifying edges on a camshaft target of an internal combustion engine rotating in a conventional direction of rotation and controlled by a control unit referred to as a “UCE”. Said camshaft target has a plurality of teeth over the periphery thereof, the plurality of teeth forming, for a position sensor facing said teeth, a series of edges when the camshaft rotates by one revolution.
Description of the Related Art
A four-stroke internal combustion engine of the most currently widespread type (intake-compression-combustion-exhaust) requires two crankshaft revolutions (the crankshaft being formed integrally with the movable equipment formed by connecting rods and pistons moving in cylinders) in order to describe the four strokes of the cycle. The camshaft, for its part, describes only a single revolution during the same four-stroke cycle. By combining (or not) the information provided by sensors associated with targets integral with the crankshaft and/or the camshaft, various items of information useful for the control of the operating parameters of the engine are obtained. The sensor associated with the crankshaft usually makes it possible to determine the exact position of the engine.
A camshaft target is used to obtain information concerning the angular position of the camshaft. In accordance with a very simple version, the target makes it possible to know whether the engine cycle is in the first or the second crankshaft revolution, the camshaft turning twice as slow and making it possible to eradicate the uncertainty concerning the position of the engine created with a position sensor placed on the crankshaft.
In more complex versions, the camshaft target can be used to perform the function known under the term “VVT”, that is to say “variable valve timing”, for which one or more camshafts can be angularly offset dynamically in relation to the nominal position thereof and thus make it possible to vary the moments of opening and closure of valves.
Lastly, a camshaft target can also be used to remedy the case in which the information obtained directly concerning the position of the crankshaft is debased or defective. In this particular case, the real-time management of the engine will be based on the information concerning the position of the camshaft obtained by means of the camshaft position sensor and the target.
It is known, for example from document U.S. Pat. No. 7,428,459, to detect the position of a camshaft target and to control the engine management tasks, such as the ignition of the fuel/oxidant mixture, the injection, and other accompanying tasks. More particularly, said document concerns the identification of the edges representing the teeth of the target at the moment of the first transitions after initialization in order to know the position of the camshaft without ambiguity.
However, in the prior art, the logic for recognition involves the implementation of an edge identification strategy that is dependent directly on the geometric profile and the position of the teeth on the periphery of the camshaft target. For an application with a camshaft target of different form, it is thus necessary to conceive a different edge identification strategy.